The invention relates to heat-resistant positive resists based upon oligomeric and/or polymeric polybenzoxazole precursor stages and diazoquinones as well as to a method for preparing heat-resistant relief structures from such positive resists.
Heat-resistant and highly heat resistant photo resists are required for cost-effective direct production of structured insulating layers. The resist materials and the corresponding relief structures must not decompose when subjected to the high temperatures used during the production of the insulating layers. Moreover, the relief structures must not be deformed upon the softening of the polymer material, rather, they must be dimensionally stable.
Conventional positive resists, for instance, on the basis of Novolaks, are suitable for use at high temperatures since they get soft in the process and the polymer chains are broken. High-temperature resistant negative resists are known, for instance, from German Patents 23 08 830 and 24 37 348, however, these resists are subject to the disadvantages which are associated with negative-performing photo varnishes, such as negative flanks, relatively long exposure times, relatively low resolution and the need to use ecologically undesirable developers.
From DE-OS 26 31 535, a heat-resistant positive resist on the basis of polyamidocarboxylic acid/diazoquinone is known. However, this positive resist has a number of disadvantages such as limited storage life, insufficient stability in alkaline etching solutions and a low solubility difference between exposed and unexposed areas.
The foregoing disadvantages are avoided if positive resists are manufactured based upon oligomeric and/or polymeric precursor stages of polyoxazoles and diazoquinones (see European Patent 0 023 662). The polyoxazole precursor stages are polycondensation products of aromatic and/or heterocyclic diaminodihydroxy compounds and dicarboxylic acid chlorides or esters. Precursor stages of polybenzoxazoles are preferred.
It is, therefore, an object of the invention to provide highly heat resistant positive resists based upon polybenzoxazole precursor stages and diazoquinones which are inexpensive to manufacture.
It is a further object of the invention to provide positive resists with a new spectrum of properties, particularly with high resolution.